Effective suppression method of three-phase transformer´s inrush current

Three-phase transformers are key components in power systems and power plants. Security, stability and increasing the life of transformers are important to system operation. When a three-phase transformer is energized, the inrush current-due to flux saturation in the core-results in a malfunction of the differential relay and also causes a stress impact to the transformer. These have an adverse effect on the security and stability of the power system. In this paper, a nonsynchronous suppressing method is proposed to suppress the inrush current of three-phase transformers. The overvoltages caused by the inrush current can also be avoided. The proposed method is examined by means of experiments, which show excellent results in suppressing the inrush current. The proposed method can be applied to improve the protective relaying system of three-phase transformers.